1. Field of the Invention
This invention relates generally to hard disk controllers and, more particularly, the invention relates to a disk controller and associated methods that enable multiple write operations to be executed out of order during a single revolution of a disk.
2. Description of the Related Art
The speed at which a hard disk drive executes read and write operations requested by a host computer is critical to the performance of the computer. Any delay caused by the hard disk drive will likely cause a corresponding delay in the execution of a program by the computer. Some of the developments in hard drive technology have focused on decreasing the response time or increasing the data transfer rate for individual disk operations. Other developments in hard drive technology have focused on decreasing the amount of time that it takes to execute multiple operations. Two of the latter type of developments are described in U.S. Pat. Nos. 4,667,286 and 6,029,226.
U.S. Pat. No. 4,667,286, titled “Method and apparatus for transferring data between a disk and a central processing unit,” presents an architecture with toggling data buffers. The architecture allows multiple operations to be performed during a single revolution of the disk. Data is transferred between the central processing unit and a first data buffer while data is transferred between a second data buffer and the disk. The operation of the buffers can be toggled such that data is transferred between the central processing unit and the second data buffer while data is transferred between the first data buffer and the disk.
U.S. Pat. No. 6,029,226, titled “Method and apparatus having automated write data transfer with optional skip by processing two write commands as a single write command,” presents a method for combining write commands. The proximity of the first logical block address (LBA) of a second write command is compared to the ending LBA of a first write command. If the second write command is sufficiently close, the disk controller executes the two write commands as a single write command, skipping over the sectors between the two commands during the combined write. Two writes, therefore, can be performed in one revolution of the hard disk.
In certain instances, it would also be advantageous to execute write operations in an order other than the order in which the operations are received by the disk controller. Executing write operations out of order may allow the writes to be executed during a single rather than multiple revolutions of the disk. The total time taken to execute the operations is therefore reduced. The present invention seeks to provide this advantage, among others.